The present invention relates to manufacturing of magnetoresistive spin valve (SV) devices. In particular, the present invention relates to a method of fabricating abutted junction SV heads for longitudinal recording.
A magnetic read head retrieves magnetically-encoded information that is stored on a magnetic medium or disc. The magnetic read head is typically formed of several layers that include a top shield, a bottom shield, and a read sensor positioned between the top and bottom shields. Also positioned between the top and bottom shields, abutting opposite sides of the read sensor, are biasing layers and current contacts. The read sensor is generally a type of magnetoresistive (MR) sensor. The resistance of the MR sensor fluctuates in response to a magnetic field emanating from a magnetic medium when the MR sensor is used in a magnetic read head and positioned near the magnetic medium. By providing a sense current through the MR sensor, the resistance of the MR sensor can be measured and used by external circuitry to decipher the information stored on the magnetic medium.
The spin valve effect is one known way to utilize magnetoresistance. Present abutted junction SV technology utilizes SV stacks with a thickness around 400 angstroms, while a combined thickness of surrounding biasing layers and current contacts is close to 1000 angstroms. This 600 angstrom difference in thickness creates a non-planar top shield topography near the sensor. For SV readers targeted at 100 kTPI and above, this top shield non-planar topography is comparable to the lateral dimensions of the reader. As a result, this non-planar topography presents serious concerns.
First, the top shield is made of soft magnetic material, which tends to break into magnetic domains in regions with corners and non-planar topography. Formation of magnetic domains in the top shield that are in close vicinity to the MR sensor is highly undesirable, because it is expected to be a source of magnetic instability and, thus, increase noise in the reader.
Second, the top and bottom shields need to shield the MR sensor from down-track transitions on the magnetic media and enable adequate electrical pulse-width (PW50), which is the width of the pulse signal at 50% peak amplitude, of the MR read sensor. These are achieved when a spacing between the bottom shield and the top shield are at a minimum. Large top shield non-planar topography is expected to compromise the shield-to-shield spacing at the edges of the sensor, thus deteriorating the down-track shielding capability and the PW50.
Third, the top and bottom shields need to shield the MR sensor from transitions in adjacent tracks on the magnetic media and provide adequate electrical reader width, which is evaluated by the MT50 and MT10 values. MT50 and MT10 values are the width of the pulse signal at 50% and 10% peak amplitude, respectively. Large top shield non-planar topography is expected to allow more flux penetration from the adjacent tracks. This will lead to deteriorated MT50/MT10 values or, alternatively, would require narrower physical reader width to achieve the required electrical reader width.
The conventional method of fabricating MR readers first defines a reader width of the MR sensor and then defines a back edge of a stripe height of the MR sensor. As will be explained below, this process creates a region of significantly thinned current contacts behind the stripe height back edge. After lapping an air bearing surface (ABS) of the MR sensor to define a stripe height front edge, the thickness of the remaining part of the current contacts is significantly reduced. Consequently, current supplied to the MR sensor through the current contacts is forced to go through two paths that have high resistance—one is a thick but narrow strip at the ABS, while the other is a wide but thin region extending behind the stripe height back edge. This creates large parasitic resistance. While this large parasitic resistance is within acceptable values when the top shield non-planar topography is 600 angstroms (contacts plus biasing layers equal to 1000 angstroms), it will become very large if the contact thickness is reduced in order to create flat top shields (contact plus biasing layers equal to 400 angstroms). Electronics associated with the MR reader are not optimized for these high resistance levels and redesigning the electronics would be too costly.
Therefore, there is a need for a method of fabricating a MR reader with top shield planar topography. Additionally, the method must be economical and minimize parasitic resistance.